Chemical mechanical polishing (CMP) is used for semiconductor wafers during the fabrication of integrated circuits. The role of the CMP is to polish or grind down semiconductor wafers in order to obtain a highly planar, scratch-free, and contamination-free surface.
Illustrated in FIG. 1, a conventional CMP apparatus 10 is illustrated in FIG. 1, which includes a polishing platen 11, a lower drive shaft 12, a polishing pad 13, a carrier 14, and an upper drive shaft 15. The lower drive shaft 12 is provided to rotate the polishing platen 11. The polishing pad 13 is attached onto the polishing platen 11. The upper drive shaft 15 is provided to rotate the carrier 14 on which a wafer 16 to be polished is placed. During polishing, aqueous slurry 17 is dripped onto the polishing pad 13 through a nozzle 21 at the end of a slurry supply system 20. The slurry 17 is a suspension, which contains abrasive particles having a size of approximately 100 nm. The abrasive particles are formed, for example, of silicon oxide, aluminum oxide, or cerium oxide.
A schematic arrangement of the slurry supply system 20 for multiple CMP apparatus 10 is illustrated in FIG. 2. The slurry supply system 20 includes a slurry reservoir 22, a slurry source pipe 23, valve manifold boxes 241-244, delivery lines 251-254, and filters 261-264. The valve manifold boxes 241-244 are provided for introducing the slurry 17 from the slurry source line 23 into the delivery lines 251-254 so as to reach the CMP apparatus 10. The slurry source pipe 23 circulates the slurry 17 thereby suppressing the formation of sedimentation and coagulation of the abrasive particle. The filters 261-264 are provided respectively on the downstream end of the delivery lines 251-254 for blocking the agglomerated particles before entering the CMP apparatus 10. Generally, for preventing the pipelines and the related filters from clogs by the agglomerated particles, the slurry supply system 20 has to be regularly flushed. The method for flushing main circulation loops (e.g. the slurry source pipe 23) has been developed as the disclosure of US Patent Application Publication No.: 2006/0043029 A1, which is incorporated herein by reference. As for flushing of the delivery lines 251-254, it is conventionally conducted one by one through a movable flushing liquid cart 27 at the place near the corresponding CMP apparatus 10. As shown in FIG. 2, the flushing is conducted by manually connecting the cart 27 with the filter 264 and then washing the end portion 254a of the delivery line 254 while the other portion of the delivery line 254 still remains unflushed for preventing the slurry source pipe 23 from contaminations. The movable flushing liquid cart 27 will forward to the next line when the flushing of the delivery line 254 is executed.
Since the conventional method for flushing the delivery lines 251-254 has to be conducted one by one, considerable operation time is consumed, which is uneconomical. In addition, the conventional method also falls to sufficiently clean all portions of the delivery line, which inevitably leads into clogs in the unflushed portions. Therefore, it would be desirable to provide an improved slurry supply system with a novel flushing function to resolve the above-described problems.